There are two current types of expansion screws with which the forces exerted by the expansion screw are to be transferred in various ways onto the tooth or teeth, the position of which is intended to be corrected: In expansion screws of a first type, the relevant expansion screw is embedded in a palate plate cast from casting resin and divides the palate plate into two parts such that one of the two expansion screw body members of the expansion screw is located in each palate plate part and so the distance of the two palate plate parts from one another can be altered by turning the threaded spindle of the expansion screw. During the casting of the palate plate, for example, clasp-like anchoring elements are secured therein and these elements engage on teeth so that the forces of the expansion screw are transferred to the relevant teeth via the palate plate parts. Such an expansion screw of this type is, for example, illustrated in FIG. 3 of DE-PS 33 01 753. With the second type of expansion screw, two rods or stiff wires are secured, in particular welded, to each of the two expansion screw body members and the relevant expansion screw body member can be anchored by these rods or wires directly onto metal bands secured to the teeth. An expansion screw of this type is illustrated, for example, in FIG. 2 of U.S. Pat. No. 4,917,601.
When in the above or in the following mention is made of a tooth adjustment or of the correction of the position of a tooth or several teeth, this is to be understood as also including, for example, the separation of the mid-palatal suture since a mid-palatal suture separation also results, of course, in an alteration of the tooth position.